1. Field of the Invention
The present invention relates generally to a trap control system including a manager and an agent which are connected via a network to each other, the agent issuing a trap to the manager, for monitoring, and more particularly, to a trap control system arranged to issue a trap to only the manager which has made an entry as an object of trap into the agent.
2. Description of the Related Art
With recent networks such as LAN expanded and complicated, the network management adds to its importance. For such a network management, use is made of various network management protocols, typically CMIP (Common Management Information Protocol) or SNMP (Simple Network Management Protocol). These management protocols basically use a polling system and an event system. In the polling system the manager asks equipment to be managed at a certain interval to check the status of the equipment to be managed at all times. This system is characterized by its correct monitoring capability but has a demerit tending to cause traffics and lacking in real-time performance. In the event system the equipment to be managed posts the manager on the variation of the status of its own. The event system serves to complement the polling system. Various restrictions are however imposed on the event system. Currently, in the field of the SNMP, typical network management protocol, the event system is called a trap. The trap is issued upon the occurrence of variation of the status from the equipment to be managed such as printers mounted with SNMP agents. The trap from the agent is accepted by a manager in order to grasp the status of the equipment to be managed. The SNMP trap issuance system can include a broadcast system and a unicast system.
FIG. 1 illustrates the broadcast system trap. Now assume that to a subnet 106 are connected an agent 100, managers 102-1 and 102-2 and hosts 104-1 and 104-2, with the agent 100 and the manager 102-1 making up a management group. Herein, the subnet 106 is e.g., a network having an address obtained by adding a 4-bit subnet to an 8-bit network ID, for the address of each node composed of the network ID and the host ID. In such a subnet 106, by using the same address for the subnet of the network ID, the management group can be composed of the agent 100 and the manager 102-1. In the ordinary state of operation the agent 100 issues a broadcast system trap. However, the broadcast trap issued from the agent 100 is accepted only by manager 102-1 lying in the network ID of the same subnet as the target of management. Nevertheless, in the broadcast system, the trap is issued to all the hosts 104-1 and 104-2 lying in the subnet 106. For this reason, traffics tend to occur within the subnet 106. In particular, recently, more and more networks employ switching techniques to control the traffics within the subnet, although there remains a problem of high ratio incapable of controlling the traffics by the broadcast trap. The broadcast issued trap acts not merely on the network traffics but also on the manager managing the trap. When the agent 100 issues a broadcast trap, the manager 102-2 not managing the agent 100 also accepts the trap. The manager 102-2 needs to seek a useful trap from the agent which is its own target of management among a multiplicity of traps accepted, resulting in an increased burden on the manager.
In order to solve such a problem of the conventional broadcast issued trap, it is conceivable to issue the trap in the unicast system. In the unicast system, a trap post manager is previously entered into each of the agents so that only the trap entered manager is posted on the trap. In case of the unicast system trap, however, the trap posted object must be entered into the agent previous to the start of use. Such entries are cumbersome and time-consuming, so that the broadcast system has eventually been employed. Furthermore, when the trap posted object is once entered, the agent continues to issue the traps till the cancellation of the entry irrespective of the manager down. Thus, in addition to the occurrence of traffics, the agent does the vain works, which may adversely affect the performances of the equipment to be managed.
Reference is then made to FIG. 2 to consider the case where the trap is issued in the unicast system with the manager 102-1 of the subnet 106 being the object of trap which is entered into the agent 100-1 to 100-n. At that time, in the event of the address modification of the manager 102-1 or the change to the manager 102-2, the entries of the object of trap have to be changed in all the agents 100-1 to 100-n. This change of entries may become enormous and fairly heavy in the circumstances including a lot of equipment to be managed. Furthermore, a limited amount of memory is provided on the equipment to be managed serving as the agent. Hence, if the entries of the object of trap unused are not deleted, more and more memories are used and the resources of the equipment to be managed are consumed.
The above problems are summarized. First, the broadcast system trap entails the problems which follow:
(I) When the trap is issued in the broadcast system, a lot of traffics occur in the network;
(II) The manager outside the subnet is unable to accept the broadcast system trap; and
(III) Due to indiscriminate sending of the broadcast trap to all the network apparatuses lying within the subnet, a heavy burden is imposed on each apparatus and managers.
Second, the unicast system trap entails the problems which follow:
(I) In case of the unicast trap, the objects of trap are previously entered, so that a burden is imposed on the manager, making it difficult to use the trap;
(II) Till the cancellation of the previously entered objects of trap, the traps are sent without managing the associated nodes by the manager;
(III) It is substantially impossible for all the entries of the objects of trap to correctly migrate when the management system configuration has been modified; and
(IV) The amount of use of the memory is increased in the equipment to be managed, owing to the entries of vain objects of trap.
Such problems may be attributable to a change in network environment being expanded and complicated. The conventional network management is directed mainly to the management of the network apparatuses such as routers and exchanges. On the network, however, there lies a less number of apparatuses such as the routers and exchanges, so that the frequency of occurrence of traffics is small irrespective of the issuance of traps in the broadcast system, thus imposing no burden on the network. In the event that there is a need to alter the setting of the objects of trap in the unicast system, it can be dealt merely by resetting a small number of hosts, and hence too a heavy burden will not occur even though it has manually been done.
The conventional information to be monitored mainly contains equipment status, especially failure information, so that less kind of information lies with limited number of traps issued. In the ordinary operation, the SNMP manager is installed on the dedicated server to manage the network equipment. On a single network the number of such SMNP managers is small and, once set and started to work, frequent change is not made. For this reason, it will suffice for the unicast system to have less information on the SMNP manager which is the object of traps to be entered into the equipment to be managed, with little or no change after the entries. Recently, however, the SNMP network management tends toward new trend together with the expanded and complicated networks. First, office apparatuses such as workstations, personal computers and printers are also managed by the SNMP, adding to the kind and number of the apparatuses to be managed. The information to be managed comes to contain not merely the conventional failure information but also information on tasks, jobs, expendable supplies in operation, for being monitored for statistics or accounting management, resulting in an enormous amount of information as compared with the past.
Furthermore, the SNMP manager monitoring a general apparatus is not a dedicated server, but is capable of being installed into a client using a general personal computer as well, with the result that the number of managers increases in unfixed status. In such an environment, employment of the broadcast system tarp may result in more serious network traffics. Alternatively, employment of the unicast system trap makes it substantially impossible to manually enter the traps one by one. A novel trap control technique is thus desired.
According to the present invention there is provided a trap control system directed to the SNMP network management and capable of improving the network performances with the minimum influences on the network, manager and agent side equipment to be managed.
The present invention is directed to a trap control system including a manager and an agent which are connected via a network to each other. In such a trap control system, according to a first aspect of the present invention the manager comprises an entry demand processing unit issuing a trap entry demand containing a self-address and trap effective time to an agent to be monitored, for the entry as an object of trap; an effective time management processing unit issuing a release demand for deleting the entry as the object of trap or issuing a time extension demand for continuing the entry as the object of trap, in response to a release validation demand from the agent; and a trap monitor processing unit receiving and processing a trap from an agent which has made an entry demand as the object of trap. The agent comprises a trap entry processing unit entering an address of the object of trap and trap effective time into a database upon the receipt of a trap entry demand from the manager; a trap issuance processing unit referring to the database upon the occurrence of trap to issue a trap to the manager entered as the object of trap; a timeout monitor processing unit issuing a release validation demand to a corresponding manager upon the timeout of the trap effective time of the database; a release processing unit deleting the entry of a corresponding object of trap in the database upon the receipt of a release demand from the manager; and a time extension processing unit updating a corresponding effective time in the database upon the receipt of a time extension demand from the manager. In this manner, the trap control system of the present invention basically issues a unicast system trap instead of a broadcast system trap whereby it is possible to reduce the amount of network traffic to allow even the managers outside the subnet to receive the trap. The manager is able to enter itself as the object of trap into an agent of equipment to be monitored, so that the manager can provide a control of whether the trap of the agent is to be received or not, preventing issuance of vain traps. The protocol between the manager and the agent enables the operations such as the entries and deletions of the objects of trap to automatically be performed without operators, to thereby relieve the burden on the operators, ensuring correct system setting for unicast trap issuance.
In the absence of any response in spite of elapse of a certain period of time after the issuance of a release validation demand to the manager, the timeout monitor processing unit of the agent deletes the object of trap which has expired from the database. By virtue of such an agent-side control of the effective time of the object of trap entered, in the event of down of the manager the agent can cancel the entered object of trap by its own judgement, making it possible to achieve an effective utilization of resources of the agent and to reduce the number of the vain traps. The trap entry demand issued from the manager contains an authentication ID for an entry as an object of trap into the database of the agent, the entry as the object of trap being deleted from the database in case of coincidence by collation of the authentication ID upon the receipt of a release demand command. This achieves improved securities of the entry and cancellation of the object of trap, enabling a substitute third party to perform the entry or deletion of the object of trap. The trap demand processing unit, the release processing unit and the time extension processing unit of the agent issue a demand success to the manager in case of having successfully processed a demand from the agent, but issues a demand failure to the manager in case of having failed to process the demand. This enables the manager to correctly grasp the situations of entries and cancellations of the object of trap in the agent, to take appropriate measures. The trap entry processing unit and the time extension processing unit of the agent have threshold values in the form of the maximum effective time and the minimum effective time of trap effective time such that coincidence with the maximum effective time is made in case the demanded effective time exceeds the maximum effective time and that coincidence with the minimum effective time is made in case the demanded effective time is shorter than the minimum effective time. By allowing this trap effective time to coincide with the maximum effective time, it is possible to obviate the entry of the object of trap exceeding the required time to prevent any unnecessary traps. By allowing the trap effective time to coincide with the minimum effective time, restriction can be imposed on the increased number of times of issuance of commands of the trap entry demand and the time extension demand arising from too short effective time.
According to a second aspect of the present invention there is provided a trap control system including a manager, an agent and a representative agent which are connected via a network to one another, the agent transferring a trap via the representative agent to the manager, for monitoring. In this system, the manager comprises a trap entry demand processing unit issuing to the representative agent a trap entry demand which contains an address of an agent to be monitored, a self-address and trap effective time, for entry as an object of trap; a time management processing unit issuing, with the designation of an agent address, a release demand for deleting the entry as the object of trap or a time extension demand for continuing the entry as the object of trap, in response to a release demand from the representative agent; and a trap monitor processing unit receiving for processing from the representative agent a trap of an agent which has made an entry demand as the object of trap. The representative agent comprises a database provided separately for each agent; a trap entry processing unit which upon the receipt of a trap entry demand from the manager, enters an address as an object of trap and effective time into a database designated by an agent address; a trap issuance processing unit referring to a corresponding database upon the post on a trap from the agent, to issue a trap to a manager entered as an object of trap; a release validation processing unit issuing a release validation demand of a corresponding agent to a manager upon the timeout of the trap effective time of the database; a release processing unit deleting the entry of a corresponding object of trap in a database designated by an agent address, upon the receipt of a release demand from the manager; and a time extension processing unit updating corresponding effective time in a database designated by an agent address, upon the receipt of a time extension demand from the manager. By virtue of such a representative agent function, even in case of the ordinary agent not having the functions of the present invention due to some reasons such as restrictions on memory resources, the trap is generated in the unicast system whose object of trap is the representative agent so that the manager can enter itself as the object of trap into the agent of equipment to substantially be monitored, to thereby control the receipt of trap from the agent.